The US department of justice has released a heavily redacted classified application from the FBI related to the surveillance of former a Trump campaign official Carter Page in 2016

President Donald Trump speaks about his summit meeting with Russian President Vladimir Putin as he begins a meeting with members of the U.S. Congress at the White House in Washington.(REUTERS File Photo)

The US department of justice has released a heavily redacted classified application from the FBI related to the surveillance of former a Trump campaign official Carter Page in 2016.

Page was under surveillance as part of a probe into whether he conspired with the Russian government to undermine the 2016 US presidential election. The application to keep him under observation were filed by the FBI under the Foreign Intelligence Surveillance Act (FISA).

The release, called historic and unprecedented in the history of the four decades of this act, came in response to right of information appeal from media organisations.

Page had served as a foreign policy adviser to the Trump campaign and has been described as someone who had “knowingly engaged in clandestine intelligence activities” on behalf of a foreign power identified as the government of the Russian federation.

Page has denied being a foreign agent.

The FISA application has become a major plank for Republicans and Trump to try and discredit the Russia probe. They argue that a dossier, put together by a former British spy for a client who wanted political dirt on Trump, was key to the FBI’s case against Page.

Democrats and the FBI have argued there were more reasons to put Page under surveillance. However, much of that evidence and details have been lost in the redaction.

But Trump, who had difficult week dealing with the fallout of his controversial news conference with Russian President Vladimir Putin in Helsinki, used the release of the document to claim vindication. “Looking more & more like the Trump Campaign for President was illegally being spied upon (surveillance) for the political gain of Crooked Hillary Clinton and the DNC,” he tweeted on Sunday.

“Ask her how that worked out... Republicans must get tough now. An illegal Scam!”

Nancy Pelosi, the top Democrat in the House of Representatives, however, said the application established “clear evidence of ‘Russia’s coordination with Carter Page’, a high-ranking Trump campaign official”.